Note that changing <varname>wal_level</varname> to

<literal>minimal</literal> makes any base backups taken before

unavailable for archive recovery and standby server, which may

lead todatabase loss.

lead todata loss.

</para>

<para>

In <literal>logical</literal> level, the same information is logged as

<listitem>

<para>

When this parameter is <literal>on</literal>, the <productname>PostgreSQL</productname>

server compressesafull pageimage written to WAL when

server compresses full pageimages written to WAL when

<xref linkend="guc-full-page-writes"/> is on or during a base backup.

A compressed page image will be decompressed during WAL replay.

The default value is <literal>off</literal>.

On the subscriber side, specifies how many replication origins (see

<xref linkend="replication-origins"/>) can be tracked simultaneously,

effectively limiting how many logical replication subscriptions can

be created on the server. Setting it a lower value than the current

be created on the server. Setting ittoa lower value than the current

number of tracked replication origins (reflected in

<link linkend="view-pg-replication-origin-status">pg_replication_origin_status</link>,

not <link linkend="catalog-pg-replication-origin">pg_replication_origin</link>)

The <xref linkend="pgstatstatements"/> extension also requires a query

identifier to be computed. Note that an external module can

alternatively be used if the in-core query identifier computation

specification isn't acceptable. In this case, in-core computation

method is not acceptable. In this case, in-core computation

must be disabled. The default is <literal>off</literal>.

</para>

<note>

<para>

To ensure thataonly one query identifier is calculated and

To ensure that only one query identifier is calculated and

displayed, extensions that calculate query identifiers should

throw an error if a query identifier has already been computed.

</para>

<returnvalue>text</returnvalue>

</para>

<para>

Evaluate escaped Unicode characters in argument. Unicode characters

Evaluate escaped Unicode characters intheargument. Unicode characters

can be specified as

<literal>\<replaceable>XXXX</replaceable></literal> (4 hexadecimal

digits), <literal>\+<replaceable>XXXXXX</replaceable></literal> (6

<returnvalue>boolean</returnvalue>

</para>

<para>

Requests to log the memory contextswhosebackendprocess has

thespecified process ID. These memory contexts will be logged at

Requests to log the memory contextsof thebackendwith the

specified process ID. These memory contexts will be logged at

<literal>LOG</literal> message level. They will appear in

the server log based on the log configuration set

(See <xref linkend="runtime-config-logging"/> for more information),

but will not be sent to the clientwhatever the setting of

but will not be sent to the clientregardless of

<xref linkend="guc-client-min-messages"/>.

Only superusers can request to log the memory contexts.

</para></entry>

<para>

<function>pg_log_backend_memory_contexts</function> can be used

to log the memory contexts ofthe backend process. For example,

to log the memory contexts ofa backend process. For example:

<programlisting>

postgres=# SELECT pg_log_backend_memory_contexts(pg_backend_pid());

pg_log_backend_memory_contexts

LOG: level: 1; ErrorContext: 8192 total in 1 blocks; 7928 free (3 chunks); 264 used

LOG: Grand total: 1651920 bytes in 201 blocks; 622360 free (88 chunks); 1029560 used

</screen>

Formore than 100 child contexts under the same parent one,

100 child contextsanda summary of the remainingones will be logged.

If there aremore than 100 child contexts under the same parent, the first

100 child contextsare logged, along witha summary of the remainingcontexts.

Note that frequent calls to this function could incur significant overhead,

because it may generate a large number of log messages.

</para>

Returns recovery pause state. The return values are <literal>

not paused</literal> if pause is not requested, <literal>

pause requested</literal> if pause is requested but recovery is

not yet paused and, <literal>paused</literal> if the recovery is

not yet paused, and <literal>paused</literal> if the recovery is

actually paused.

</para></entry>

</row>

any changes that happened during the initial data copy using standard

logical replication. During this synchronization phase, the changes

are applied and committed in the same order as they happened on the

publisher. Oncethesynchronization is done, the control of the

publisher. Once synchronization is done, control of the

replication of the table is given back to the main apply process where

thereplication continues as normal.

replication continues as normal.

</para>

</sect2>

</sect1>

</para>

<para>

The subscriber also requires the <varname>max_replication_slots</varname>

be set to configure how many replication origins can be tracked. In this

case it should be set to at least the number of subscriptions that will be

added to the subscriber, plus some reserve for table synchronization.

<varname>max_replication_slots</varname> must also be set on the subscriber.

It should be set to at least the number of subscriptions that will be added

to the subscriber, plus some reserve for table synchronization.

<varname>max_logical_replication_workers</varname> must be set to at least

the number of subscriptions, again plus some reserve for the table

synchronization. Additionally the <varname>max_worker_processes</varname>

never issue <command>VACUUM FULL</command>. In this approach, the idea

is not to keep tables at their minimum size, but to maintain steady-state

usage of disk space: each table occupies space equivalent to its

minimum size plus however much space gets used up betweenvacuumings.

minimum size plus however much space gets used up betweenvacuum runs.

Although <command>VACUUM FULL</command> can be used to shrink a table back

to its minimum size and return the disk space to the operating system,

there is not much point in this if the table will just grow again in the

</para>

<para>

When creating an index on a partitioned table, this column is set to

the number of partitions on which the index has beencompleted.

the number of partitions on which the index has beencreated.

This field is <literal>0</literal> during a <literal>REINDEX</literal>.

</para></entry>

</row>

<xref linkend="guc-max-wal-senders"/> to zero.

But note that changing these settings requires a server restart,

and makes any base backups taken before unavailable for archive

recovery and standby server, which may lead todatabase loss.

recovery and standby server, which may lead todata loss.

</para>

<para>

much faster. The following are configuration changes you can make

to improve performance in such cases. Except as noted below, durability

is still guaranteed in case of a crash of the database software;

only abrupt operating systemstoppage creates a risk of data loss

onlyanabrupt operating systemcrash creates a risk of data loss

or corruption when these settings are used.

<itemizedlist>

<note>

<para>

The following details about constant replacement and

<structfield>queryid</structfield> onlyapplies when <xref

<structfield>queryid</structfield> onlyapply when <xref

linkend="guc-compute-query-id"/> is enabled. If you use an external

module instead to compute <structfield>queryid</structfield>, you

should refer to its documentation for details.

<title>Connection Management Options</title>

<para>

By default all the open connections that <filename>postgres_fdw</filename>

established to the foreign servers are kept in local session for re-use.

By default, all connections that <filename>postgres_fdw</filename>

establishes to foreign servers are kept open in the local session

for re-use.

</para>

<variablelist>

<listitem>

<para>

This option controls whether <filename>postgres_fdw</filename> keeps

the connections to the foreign server open so thatthesubsequent

the connections to the foreign server open so that subsequent

queries can re-use them. It can only be specified for a foreign server.

The default is <literal>on</literal>. If set to <literal>off</literal>,

all connections to this foreign server will be discarded at the end of

transaction.

eachtransaction.

</para>

</listitem>

</varlistentry>

</listitem>

</varlistentry>

<varlistentry id="reloption-autovacuum-vauum-scale-factor" xreflabel="autovacuum_vacuum_scale_factor">

<varlistentry id="reloption-autovacuum-vacuum-scale-factor" xreflabel="autovacuum_vacuum_scale_factor">

<term><literal>autovacuum_vacuum_scale_factor</literal>, <literal>toast.autovacuum_vacuum_scale_factor</literal> (<type>floating point</type>)

<indexterm>

<primary><varname>autovacuum_vacuum_scale_factor</varname> </primary>

</listitem>

</varlistentry>

<varlistentry id="reloption-autovacuum-vauum-cost-limit" xreflabel="autovacuum_vacuum_cost_limit">

<varlistentry id="reloption-autovacuum-vacuum-cost-limit" xreflabel="autovacuum_vacuum_cost_limit">

<term><literal>autovacuum_vacuum_cost_limit</literal>, <literal>toast.autovacuum_vacuum_cost_limit</literal> (<type>integer</type>)

<indexterm>

<primary><varname>autovacuum_vacuum_cost_limit</varname></primary>

If you wish to create a new superuser, you must connect as a

superuser, not merely with <literal>CREATEROLE</literal> privilege.

Being a superuser implies the ability to bypass all access permission

checks within the database, sosuperuserdom should not be granted lightly.

checks within the database, sosuperuser access should not be granted lightly.

</para>

<para>